Vehicles incorporating multiple drive axles benefit in many ways over vehicles having a single driven axle. Drive axle systems in such vehicles may be configured to distribute torque between the axles, increasing tractive effort. The incorporation of an inter-axle differential allows the torque to be distributed between multiple axles while providing each axle operating flexibility. Power is typically applied to such drive axle systems through a Cardan shaft in driving engagement with both a transmission of the vehicle and the drive axle system.
FIG. 1 illustrates a conventional drive axle system 100. The drive axle system 100 includes an input shaft 102, an inter-axle differential 104, a differential output gear 106, an output 108, a drop gear 110, a drive pinion 112, and an axle differential assembly 114. The drive axle system 100 is in driving engagement with a vehicle transmission (not shown) through a Cardan shaft 116 and companion flange 118, which is in splining engagement with the input shaft 102. In response to rotation of the Cardan shaft 116, the companion flange 118 rotates the input shaft 102, driving the inter-axle differential 104. The inter-axle differential 104 drives both the differential output gear 106 and the output 108. The differential output gear 106 drives the axle differential assembly 114 through the drop gear 110 and the drive pinion 112 and the output 108 drives a second axle assembly (not shown).
As shown in FIG. 1, the companion flange 118 is secured to the input shaft 102 using a fastener 120, such as, but not limited to, a nut. During assembly of a vehicle drivetrain (partially shown) including the conventional drive axle system 100, the companion flange 118 is first secured to the input shaft 102. Next, a second companion flange (not shown), or a similar fitting, is secured to an output shaft of the vehicle transmission. Lastly, the Cardan shaft 116, which is configured with a slip joint 122, is coupled to both the companion flange 118 (through the use of a bearing cross 123 and bearing straps 124) and the second companion flange, completing a connection between the vehicle transmission and the conventional drive axle system 100.
While the Cardan shaft 116 allows adequate power to be transferred from the vehicle transmission to the drive axle system 100, the Cardan shaft 116 is not without its disadvantages. Incorporation of the slip joint 122, which is necessary in most applications, increases a cost and a complexity of the Cardan shaft 116. The companion flange 118 and the second companion flange, used to join the Cardan shaft 116 with the vehicle transmission and the drive axle system 100, further complicate the vehicle drivetrain. Installation of the companion flange 118 and the second companion flange prior to attachment of the Cardan shaft 116 is laborious, and therefore increases a cost of the drive axle system 100. Further, the companion flange 118 and the second companion flange are sizeable components of the vehicle drivetrain, and contribute to increased weight of and increased noise, vibration and harshness of the vehicle drivetrain.
It would be advantageous to develop an input arrangement for a drive axle system that eliminates a need for a companion flange, reduces a weight of the drive axle system, and reduces noise, vibration and harshness associated with conventional drive axle systems.